Posted September 27, 2008
Choosing the right HDTV is difficult. One important consideration is to know how much resolution a particular HDTV extracts from a 1080i high definition signal. The HD Guru put 125 2008 HDTVs (plus one 2009 prototype) through a series of test signals to learn how different brands and models really perform. The specific results appear in the 2008 Resolution Tests PDF link below. Here is a brief rundown of these tests. For more testing information please refer to my previous articles that appeared in Home Theater magazine. You can find them at:
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Deinterlacing Test
All LCD flat panels, microdisplay rear projectors and most plasma HDTVs are progressive displays, meaning they (should) process all 1080 lines within a 1080i signal and display them at a set’s native resolution. (1080i is the broadcast standard for most HDTV networks including CBS, NBC, CW and HBO.) This is accomplished by deinterlacing the interlaced broadcast signal into one that’s scanned progressively. An HDTV that does not properly deinterlace the signal will only process a single field, reducing vertical resolution to 540 lines. Last year the HD Guru tested 74 2007 models and found that slightly fewer than 65 percent passed this test. This year’s sets fared much better with 96% of the 125 HDTVs passing!
The deinterlace test was conducted using the Silicon Optix HQV HD test disc. You can purchase this disc in the Blu-ray or HD DVD format, at a 25% discount through a coupon. Information on how to order and the coupon code can be found at www.hdguru.com/?p=153.
3:2 Tests
Most scripted television programs and almost all movies are filmed at 24 frames per second. 1080i broadcasts require that the 24 frames be split into two fields that must be recombined in the proper sequence in order to produce a 1080p signal that is artifact-free and retains full resolution.
The Silicon Optix HD HQV disc also includes a test of this key performance parameter. Last year’s results were disappointing with only 14 out of 74 sets passing (18.91%). The 2008 models showed a slight improvement with 29 out of 125 sets (23.2%) properly handling the signal. Only 1 out of 28 Samsung models passed this test and the model that passed (LN-46A950) only did so after the set’s two anti-motion blur features were shut off. Activation of either of the anti-motion blur circuits caused the set to fail.
Upon learning of the high failure rate, a Samsung spokesperson claimed newer production models of these sets will pass the test and that a downloadable firmware update, available now for owners of the failing earlier production units, fixes the problem.
(HD Guru policy is to report the results obtained, dealers sold a number these models without the latest firmware and many units may remain in their current inventory). Testing occurred between July and September 2008. The HD Guru will try to obtain samples loaded with the new firmware to confirm Samsung’s claims. If confirmed, the article and chart will be updated.
One LG’s plasma TV passed and two failed. An LG spokesperson indicated a running production change might have affected the test results. If there was any change (such as a firmware upgrade or special setting needed), it will be tested as well.
Bandwidth Tests
Can a 1080p HDTV resolve all horizontal detail down to a single pixel (out of 1920 pixels across)? To perform this test, I used a Sencore 403 HDTV signal generator with a pattern that has vertical alternating black and white lines, one pixel wide. If a set passes this test, every vertical line should be clearly visible (as black and white). If there is some roll off in bandwidth, the lines appear as dark gray and light gray. If an HDTV was unable to resolve down to a single pixel, the area of the screen would appear blank. Out of the 76-1080p sets tested, 68 displayed full bandwidth (one Philips was not tested due to its inability to sync with the Sencore generator). The remaining 1080p HDTVs exhibited some signal roll off. Note: all bandwidth, static and motion resolution tests were only performed on displays that are 1920 x 1080 “full HD†resolution. Displays with lower resolution, for example 1366×768 (listed as 768p in the chart), cannot fully resolve a 1080i HD signal.
Static and Motion Resolution
An HDTV may resolve a stationary test signal at full bandwidth, displaying all the detail within the 1920 individual pixels that appear across the screen, but not necessarily when motion is introduced, which on some sets causes a resolution drop. This can significantly degrade your viewing experience, especially if you watch a great deal of sports and/or action-oriented movies. How much resolution loss occurs? To find out, I used a test tool called the FPD Benchmark Software for the Professional.
This Blu-ray disc contains a Monoscope pattern (pictured above) which is made up of a series of four black lines that gradually come together in a wedge-like pattern that appears at the top, bottom and sides. Numbers adjacent to the lines indicate resolution. There are both stationary and moving versions of the pattern. In both instances, a number corresponds to the location of where all four lines can still be distinguished as they converge. The maximum resolution is 1080 lines “per picture heightâ€Â. If you want to calculate how many pixels a given display can resolve across the screen, simply multiply the resolution number by 1.77777.
Results
The motion resolution winner, displaying all 1080 lines through processes called motion interpolation (used on all 120Hz LCD panels) and sequential LED backlight control (called Motion Plus) was the Samsung LN-46A950. It is the only display ever tested that resolved 100% of the moving image’s detail. Congratulations to Samsung’s engineering team for eliminating motion blur on an LCD display! Please note: this performance level resulted from activating the display’s Motion Plus control and setting the interpolation (called Auto Motion by Samsung) to “low.†Any other combination of the motion control settings resulted in motion blur, dropping the perfect 1080 line score down to as low as 330 lines!
The next highest motion resolution results came from plasma HDTVs. The best 2008 models were the two Pioneer plasmas at 900 lines, followed by the other plasma displays, with results in a range of 800-850 lines. (The 150†Panasonic plasma prototype scored 920 out of 1080 lines).
Moving down the list are the 120Hz LCD flat panels. The results ranged from 550-620 lines of motion resolution, depending on the make and model of the display.
The lowest “motion resolution†group of displays were the 60 Hz LCD flat panels with a maximum of just 340 lines out of 1080. The biggest “loser†of resolution goes to the 37†Sharp LC-37D64U, recording just 260 lines out of 1080 on the Motion test, a disappointing 75%+ loss of resolution. The lone rear projector tested was a Samsung DLP. It joins this group with 330 lines of motion resolution.
Use the chart attached to this article to help you make an informed decision when choosing a new HDTV. While other factors such viewing angle and color reproduction are also important to consider when shopping for a new display, excellent image resolution provides the “high†in high definition TV viewing
2008-resolution-tests-125-hdtvs.pdf
Copyright ©2008 Gary Merson/HD Guru® All rights reserved. HD GURU is a registered trademark. The content and photos within may not be distributed electronically or copied mechanically without specific written permission.
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